Conventionally, in production facilities for semiconductor devices and so on, articles to be transported, for example, transport containers that contain works such as semiconductor substrates may be sequentially transported between multiple processing units while being held by overhead carriages (transport devices) that travel along a traveling rail provided near the ceiling of a facility.
For example, Japanese Patent Laid-Open No. 2004-25427 discloses a transport device that transports works to processing units while traveling between the processing units in a clean room. The transport device includes an elevating unit that is provided on a horizontal movement unit and vertically moves a work holding unit for holding a work (enclosed container), transferring the works between the work holding unit and the processing units.
In the transport device of Japanese Patent Laid-Open No. 2004-25427, the work holding unit includes a work holding part extended in a channel shape to two sides of a work (enclosed container). The work holding unit holds the work (enclosed container) with opposed hands provided on the lower ends of two sides of the work holding part so as to hold the bottom of the work.
In production facilities for semiconductor devices and so on, articles to be transported, for example, transport containers that accommodate works such as semiconductor substrates may be transported (in a stacked state) in which the multiple articles to be transported are stacked. Specifically, a plurality of plate-like pallets (transport containers) accommodating works are stacked and then are transported while being held (grasped) by a transport device.
In transportation of stacked articles to be transported, however, the articles to be transported are not always neatly stacked (in alignment) and thus in some cases, the stacked articles need to be transported without being aligned (out of alignment). Hence, if articles to be transported are stacked without being aligned, unfortunately, the stacked articles to be transported may be insufficiently held (grasped) by a holding (grasping) device. Moreover, the stacked articles to be transported may be disadvantageously displaced and dropped from the transport device during transportation.
Such a problem can be solved by providing an article to be transported with a displacement preventing mechanism for preventing a displacement (for example, articles to be transported may have uneven surfaces that allow engagement between the stacked articles). Unfortunately, the provision of the displacement preventing mechanism for an article to be transported may lead to a complicated configuration. Moreover, some articles to be transported cannot be provided with the displacement preventing mechanism.
Alternatively, the problem can be solved by providing securing members that secure stacked articles to be transported. Articles to be transported need to be secured with the securing members before being transported, disadvantageously leading to low working efficiency.
An object of the present invention is to provide a transport device that can transport, without changing the device configuration, stacked articles to be transported, and can correct and prevent a displacement of the stacked articles with a simple configuration.